The present invention relates to a supporting device for supporting a plastic lens in a lens supporting sleeve.
One known lens supporting device uses a pressing ring structure. That is, a stepped portion is formed inside the lens supporting sleeve for defining the position of the lens, and the lens is secured by screwing the pressing ring into threads in the lens supporting sleeve and pressing the lens against the stepped portion. Also known is a flange structure, wherein a flange portion is formed on an outer periphery of the plastic lens, and this flange portion is screwed to the lens supporting sleeve with a fixing screw. With the aforementioned structures, an extra securing member (the lens pressing ring or fixing screw) is necessary. Accordingly, production, control, and assembly for the parts becomes complicated. With the former construction, the size in the axial direction increases, and with the latter, the size in the radial direction increases, so it is difficult to make the lens compact. Also known are structures using adhesion or welding to fix a lens. The use of adhesives increases the overall cost, and assembling workability is poor. If welding is used, a welding machine must be included in the assembly process. Furthermore, welding is difficult to control, often creating defects.